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Fracture of Coffin Bone, Generally

Synonyms: Pedal Bone, P3 Fracture, Fractured Distal Phalanx

The coffin bone is the lowest bone in the horse’s leg and is also known as P3, Distal Phalanx and the Pedal Bone. It is encased in the hoof capsule (as if in a coffin) and is attached to the inner wall of the hoof by the laminae.

Fracture of the coffin bone usually occurs in a front foot when a horse steps on a rock or there is a drastic concentration of force to a small area of the sole, usually at speed. This injury can also occur to a hind foot. Hind P3 fracture can also happen when a horse kicks a solid object like a concrete stall wall.

Coffin bone fractures are classified by numeric type. These include: (1) non-articular wing fractures, (2) articular wing fractures, (3) mid-saggital articular fractures, (4) extensor process fractures, (5) solar margin fractures; and (6) non-articular foal fractures.

n general the severity of P3 fractures depends on their location, and especially whether they extend into the coffin joint. If the joint (articular surface) is involved, permanent joint damage in the form of coffin joint arthritis (low ringbone) probably will result in chronic lameness without surgical repair.

Solar margin fractures often accompany other conditions such as sole bruises, pedal osteotis, chronic laminitis or osteomyelitis. The marginal fractures seen on an x-ray are more a sign of these other conditions than they are a cause of lameness in themselves.

DIAGNOSTICS

Diagnosis is usually by clinical exam, blocking and x-ray. If a coffin bone fracture is suspected but not found in radiographs, vets often wait a few days to a week to re-radiograph the area. At that time, the fracture may be better visualized due to bone demineralization.

TREATMENT

Repair, treatment options, length of convalescence and prognosis all depends on the specific type of fracture sustained. While some coffin bone fractures may require surgical removal of bone or the placement of surgical implants, others may only require corrective shoeing and rest. If the joint is involved, surgery is more likely needed to allow healing of joint surfaces in normal alignment. In addition, joint injection of medications may be part of the treatment.

In horses that are severely lame, ample pain management is critical to ensure that the horse does not develop support limb laminitis in the opposite leg.

Prognosis & Relevant Factors

The prognosis and treatment plan depends to a great extent on the type. The prognosis is guarded to good for fractures that do not enter the joint. But even simple fractures can take up to 9 months to heal completely and may still appear as a fracture line on a radiograph.

The prognosis mostly depends on whether or not the fracture line extends into the joint surface, and the degree of arthritis that develops afterwards.

Generally, hind limb coffin bone fractures have a better prognosis than forelimb fractures.

The prognosis is good for coffin bone fractures in foals (if they do not involve the joint.)

QUESTIONS TO ASK MY VET

  • What type of fracture is this, and does it involve the coffin joint?
  • Can the problem be managed conservatively, or does the best option require surgery?
  • PREVENTION

    Stable horses to reduce the likelihood of their kicking walls. If this is habitual, some sort of wall padding may be necessary. Avoid galloping horses through rocks when possible.

    Helpful Terms & Topics in HSVGWritten, Reviewed or Shared by Experts in Equine Health

    Author: Doug Thal DVM Dipl. ABVP

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